The present invention relates to an electrostatic chuck and a substrate temperature adjusting-fixing device, and more particularly, to an electrostatic chuck for adsorbing an adsorption object placed on a base body and a substrate temperature adjusting-fixing device.
In the past, a coating device (for example, a CVD device, a PVD device, and the like) or a plasma etching device used to manufacture a semiconductor unit such as an IC or an LSI has a stage for holding a substrate within a vacuum treatment chamber with high precision. As such a stage, for example, a substrate temperature adjusting-fixing device having an electrostatic chuck is proposed.
The substrate temperature adjusting-fixing device holds the substrate in an adsorption state by using the electrostatic chuck and controls a temperature of the substrate held in an adsorption state to be a predetermined temperature. An example of the electrostatic chuck includes a coulombic-force electrostatic chuck and a Johnsen-Rahbek-force electrostatic chuck. In the coulombic-force electrostatic chuck, a response of an adsorption force is excellent with respect to an application of a voltage. However, an application of a high voltage is required and a sufficient adsorption force cannot be obtained when a contact area between the electrostatic chuck and the substrate is not large. In the Johnsen-Rahbek-force electrostatic chuck, it is necessary to flow a current to the substrate, but it is possible to obtain the sufficient adsorption force even when the contact area between the electrostatic chuck and the substrate is small.
FIG. 1 is a top view simply showing a substrate temperature adjusting-fixing device 100 according to a conventional art. FIG. 2 is a cross sectional view simply showing the substrate temperature adjusting-fixing device 100 according to the conventional art when taken along the line A-A shown in FIG. 1. As shown in FIGS. 1 and 2, the substrate temperature adjusting-fixing device 100 includes an electrostatic chuck 101, an adhesive layer 105, and a base plate 106. The electrostatic chuck 101 is a coulombic-force electrostatic chuck having a base body 102 and an electrostatic electrode 103. The base body 102 is fixed onto the base plate 106 via the adhesive layer 105. The base body 102 is formed of ceramic.
The outer edge portion of an upper surface 102a of the base body 102 is provided with an outer peripheral seal ring 102b corresponding to an annular protrusion portion in a top view. On the inside of the outer peripheral seal ring 102b in a top view, a plurality of cylindrical protrusion portions 102c is dotted in a polka-dot pattern in a top view. The heights h1 of the upper surfaces of the outer peripheral seal ring 102b and the plurality of protrusion portions 102c are the same as each other, and the height h1 may be, for example, in the range of 20 to 40 μm. The diameter φ1 of the upper surface of each protrusion portion 102c may be, for example, in the range of 1.0 to 2.0 mm.
The electrostatic electrode 103 is a thin-film electrostatic electrode and is embedded in the base body 102. The electrostatic electrode 103 is connected to a DC power source (not shown) provided in the outside of the substrate temperature adjusting-fixing device 100 and holds an adsorption object such as a substrate (not shown) in the upper surfaces of the outer peripheral seal ring 102b and the plurality of protrusion portions 102c in an adsorption state upon being applied with a predetermined voltage. The adsorbing-holding force becomes stronger as the voltage applied to the electrostatic electrode 103 becomes larger.
The base plate 106 is used to support the electrostatic chuck 101. The base plate 106 is provided with a heater (not shown) and a water path 104, thereby controlling a temperature of the base body 102. The heater (not shown) is heated upon being applied with a voltage and heats the base body 102 via the adhesive layer 105.
The water path 104 includes a cooling water introduction portion 104a and a cooling water discharge portion 104b formed in a lower surface 106b of the base plate 106. The cooling water introduction portion 104a and the cooling water discharge portion 104b are connected to a cooling water control device (not shown) provided in the outside of the substrate temperature adjusting-fixing device 100. The cooling water control device (not shown) introduces the cooling water from the cooling water introduction portion 104a into the water path 104 and discharges the cooling water from the cooling water discharge portion 104b. By circulating the cooling water to cool the base plate 106, the base body 102 is cooled via the adhesive layer 105.
A gas path 108 is formed through the base body 102, the adhesive layer 105, and the base plate 106. The gas path 108 includes a plurality of gas introduction portions 108a formed in the lower surface 106b of the base plate 106 and a plurality of gas discharge portions 108b formed in the upper surface 102a of the base body 102. The plurality of gas introduction portions 108a is connected to a pressure control device (not shown) provided in the outside of the substrate temperature adjusting-fixing device 100. The gas pressure control device (not shown) is capable of changing a pressure of an inert gas within a range, for example, 0 to 50 Torr and of introducing the inert gas from the gas introduction portion 108a to the gas path 108.
FIG. 3 is a cross sectional view simply showing a state where the substrate temperature adjusting-fixing device 100 according to the conventional art holds a substrate 107 in an adsorption state. In the same drawing, the same reference numerals are given to the same components as those of FIGS. 1 and 2, and the description thereof will be omitted. In FIG. 3, Reference numeral 107 denotes a substrate and Reference numeral 109 denotes a gas filling portion into which the inert gas is filled. As shown in FIG. 3, the substrate 107 is held in the upper surfaces of the plurality of protrusion portion 102c and the outer peripheral seal ring 102b of the base body 102. A temperature of the substrate 107 is controlled by the heater (not shown) or the water path 104 embedded in the base plate 106.
The gas pressure control device (not shown) introduces the inert gas from the plurality of gas introduction portions 108a to the gas path 108. When the introduced inert gas is discharged from the gas discharge portions 108b and is filled into the gas filling portion 109 corresponding to a space formed between the substrate 107 and the upper surface 102a of the base body 102, the heat conductivity between the base body 102 and the substrate 107 is improved. The outer peripheral seal ring 102b is provided to prevent the inert gas filled in the gas filling portion 109 from leaking to the outside of the gas filling portion 109.
As described above, the substrate temperature adjusting-fixing device 100 according to the conventional art holds the substrate 107 in the upper surfaces of the plurality of protrusion portions 102c and the outer peripheral seal ring 102b of the base body 102 of the electrostatic chuck 101 in an adsorption state. Additionally, the outer peripheral seal ring 102b as the annular protrusion portion in a top view provided in the outer edge portion of the upper surface 102a of the base body 102 of the substrate temperature adjusting-fixing device 100 according to the conventional art prevents the inert gas filled in the gas filling portion 109 from leaking to the outside of the gas filling portion 109 in order to improve the heat conductivity between the base body 102 and the substrate 107. Additionally, the heater (not shown) or the water path 104 embedded in the base plate 106 of the substrate temperature adjusting-fixing device 100 according to the conventional art controls the temperature of the substrate 107 (for example, see Patent Document 1).
As another example of the substrate temperature adjusting-fixing device according to the conventional art, there is proposed a substrate temperature adjusting-fixing device having a Johnsen-Rahbek-force electrostatic chuck, in which the outer peripheral seal ring 102b as the annular protrusion portion in a top view is provided in the outer edge portion of the upper surface 102a of the base body 102, and the plurality of cylindrical protrusion portions 102c is dotted in a polka-dot pattern in a top view on the inside of the outer peripheral seal ring 102b in a top view in the same manner as the substrate temperature adjusting-fixing device 100 shown in FIG. 1 so that the diameter φ1 of the upper surface of the plurality of protrusion portions 102c is set as small as possible and hence the contact area between the substrate 107 and the upper surface of the plurality of protrusion portions 102c is made to be small (for example, see Patent Document 2).    [Patent Document 1] JP-A-2000-317761    [Patent Document 2] JP-A-2005-33125
However, in the substrate temperature adjusting-fixing device 100 according to the conventional art, since the contact area between the substrate 107 and the upper surfaces of the plurality of protrusion portions 102c and the outer peripheral seal ring 102b is large, a problem arises in that particles are easily attached to an opposite surface of the substrate 107 contacting with the upper surfaces of the plurality of protrusion portions 102c and the outer peripheral seal ring 102b. 
As disclosed in Patent Document 2, although it is possible to reduce the particles attached to the opposite surface of the substrate 107 at a portion contacting with the upper surface of the plurality of protrusion portions 102c in such a manner that the diameter φ1 of the upper surface of the plurality of protrusion portions 102c provided in the upper surface 102a of the base body 102 is set as small as possible to decrease the contact area between the substrate 107 and the upper surface of the plurality of protrusion portions 102c, it is observed that most of particles are attached to the opposite surface of the substrate 107 at a portion contacting with the upper surface of the outer peripheral seal ring 102b. As a result, it is not possible to solve the problem that the particles are easily attached to the opposite surface of the substrate 107 just by making the diameter φ1 of the upper surface of the plurality of protrusion portions 102c as small as possible.